Which of the following is used as a recombination vector?

Refer to the following statements for agarose-gel electrophoresis :
$(a)$ Agarose is a natural polymer obtained from sea-weed.
$(b)$ The separation of $DNA$ molecules in agarose-gel electrophoresis depends on the size of $DNA$.
$(c)$ The $DNA$ migrates from negatively-charged electrode to the positively-charged electrode.
$(d)$ The $DNA$ migrates from positively-charged electrode to the negatively-charged electrode.
Choose the most appropriate answer from the options given below :

How many antibiotic resistance genes are present in $pBR322$?

In the $pBR322$ plasmid,the ampicillin and tetracycline resistance genes contain recognition sites for how many restriction enzymes,respectively?

What type of biological molecules are cloning vectors?

$I.$ Bacteriophages are $...A...$ infecting $...B....$
$II. ...C...$ are hybrid vectors derived from plasmids which contain $cos$ site of $\lambda$ phage.
$A, B$ and $C$ in above statements refer to: